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Sonic doom: Noise in pictures

High-level, constant noise can affect mental and physical well-being. From the noisiest job to the quietest place on Earth, New Scientist takes a look at the problems noise causes and how we can keep things quieter.

City sounds

Noise pollution in cities can come from many sources, but the main offenders are motor vehicles: the sound of a horn can reach up to 90 decibels.

European Union legislation has set 65 decibels as the maximum acceptable limit of continuous noise a person can tolerate on a daily basis; noise above that level affects health and mental well-being.

(Image: Scott E. Barbour/Getty)

Occupational hazard

Coal mining is particularly prone to dangerous amounts of noise: a World Health Organization study reported that 90 per cent of coal miners develop some sort of hearing impairment by the age of 52, and it is estimated that 70 per cent of male miners of all kinds will have a hearing impairment by the age of 60.

(Image: KeystoneUSA-ZUMA/Rex Features)

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The city never sleeps

Maps like this show the ambient noise environment across large urban areas. Commissioned by the UK government's environment department, this noise map of Greater London helps inform noise management policy.

The loudest sites on the map are in red and correspond to busy roads. The M4 motorway, which runs west out of London, measured an average of over 75 decibels.

Noise barriers are another effective method of mitigating road, railway and industrial noise. Acoustic walls are often used to absorb or deflect noise, but innovative structures such at the Sound Tube (left) on Melbourne's busy CityLink system help turn architectural designs into functional structures.

The steel frames that make up the Sound Tube block the direct travel of sound waves to adjacent high-rise buildings.

Phononic future

Phononic crystals are created by arranging elements, in this case metal pipes, to control the flow of sound. The position and size of these elements prevent selected frequencies from being transmitted through the material. When researchers from the Institute of Materials Science in Madrid, Spain, tested the acoustic properties of Órgano 18 years after its creation, they found it made a good phononic crystal.

Research is now under way at the UK's Transport Research Laboratory to see if modified structures like this can be used to cut noise along roads and railways.

(Image: Eusebio Sempere/Fundación Juan March)

The quietest place on Earth

Anechoic chambers are designed to be acoustically perfect. No sound reflects from the walls, floor or ceiling, and they are insulated from exterior noise. Because of this they are ideal places to test loudspeakers or microphones and for virtual acoustics – the recreation of concert hall, city street and other spaces' acoustics.

In 2004, the Guinness Book of World Records proclaimed the anechoic chamber at Orfield Laboratories in Minneapolis, Minnesota, the quietest place on Earth. It was measured at -9.4 decibels. The decibel unit describes a ratio of sound pressure and the standard reference level is set at the sensitivity of the human ear, so a negative level means a sound has a pressure too small to hear – to us, this would seem like absolute silence.